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SQL Syntax

12 min Beginner

SQL follows a unique set of rules and guidelines called syntax. This tutorial gives you a quick start with SQL by listing all the basic SQL syntax.

Database Tables

A database most often contains one or more tables. Each table is identified by a name (e.g., "Customers" or "Orders"), and tables contain records (rows) with data.

Example - Customers Table

CustomerID CustomerName ContactName City Country
1 Alfreds Futterkiste Maria Anders Berlin Germany
2 Ana Trujillo Ana Trujillo México D.F. Mexico

SQL Statements

Most of the actions you need to perform on a database are done with SQL statements.

The following SQL statement selects all the records in the "Customers" table:

Example

SELECT * FROM Customers;
Tip: SQL keywords are NOT case sensitive: select is the same as SELECT. However, it's a common convention to write SQL keywords in uppercase.

Semicolon after SQL Statements?

Some database systems require a semicolon at the end of each SQL statement.

Semicolon is the standard way to separate each SQL statement in database systems that allow more than one SQL statement to be executed in the same call to the server.

SELECT * FROM Customers;

Most Important SQL Commands

  • SELECT - extracts data from a database
  • UPDATE - updates data in a database
  • DELETE - deletes data from a database
  • INSERT INTO - inserts new data into a database
  • CREATE DATABASE - creates a new database
  • ALTER DATABASE - modifies a database
  • CREATE TABLE - creates a new table
  • ALTER TABLE - modifies a table
  • DROP TABLE - deletes a table
  • CREATE INDEX - creates an index (search key)

SQL Statement Syntax

SELECT

SELECT column1, column2, ... FROM table_name;

SELECT DISTINCT

SELECT DISTINCT column1, column2, ... FROM table_name;

WHERE

SELECT column1, column2, ... FROM table_name WHERE condition;

ORDER BY

SELECT column1, column2, ... FROM table_name ORDER BY column1, column2, ... ASC|DESC;

INSERT INTO

INSERT INTO table_name (column1, column2, column3, ...) VALUES (value1, value2, value3, ...);

UPDATE

UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition;

DELETE

DELETE FROM table_name WHERE condition;
Important: Be careful when updating or deleting records! If you omit the WHERE clause, ALL records will be updated or deleted!

Try It Yourself